Isopropanol is a very useful intermediate in organic synthesis as well as a commercially important solvent.
Acetone is produced in large amounts as a by-product in the manufacture of phenol by the cumene process. In a cumene process benzene is alkylated with propene and/or isopropanol to synthesize cumene, cumene is oxidized into cumene hydroperoxide and cumene hydroperoxide is acid cleaved to generate phenol and acetone. The acetone produced by this cumene-process contains benzene. As indicated in for example EP-A-0434485, the production of acetone in the cumene process is considered a disadvantage because the demand for phenol increases much faster than the demand for acetone. Therefore it is suggested in EP-A-0434485 to hydrogenate acetone, obtained in the cumene process into isopropanol, and recycle the isopropanol into the cumene process.
EP-A-0434485 does not describe the presence of benzene in the acetone generated by the cumene process.
The hydrogenation of benzene is much more difficult than the hydrogenation of acetone. This is illustrated, for example, by an article by E. de Ruiter and J. C. Jungers, Bull. Soc. Chim. Belg., 58 page 230, 1949, where it is stated that when a mixture of acetone and benzene is hydrogenated the acetone reacts first.
Recently it has become desirable to convert acetone, obtained in the cumene process, into isopropanol which can be used for other purposes than the recycle into the cumene process. The presence of any amounts of benzene, however, makes it disadvantageous to use the isopropanol for any purpose other than recycling to the cumene process.
The removal of traces of benzene from acetone by distillation is very difficult. Removal of benzene from isopropanol after hydrogenation is even more difficult because of the close boiling points of benzene and isopropanol.